Cutting device for buttonhole-or other sewing machines



NOV. 30, 1937. H, PUDELKQ Y Z'l CUTTING- DEVICE .FOR BUTTOEQLE- QR THER SEWING MGHINES y A Filed Sept. 24, 1934 Patented Nov. 3o, 1937 UNITED STATES cu'r'rmo DEVICE Foa U'r'roNHoLEf on oTIIEa SEWING MACHINES Hermann Pudelko, Bielefeld, Germany, assigner to Drkoppwerke Aktiengesellschaft, Bielefeld,

Germany Application September 24, 1934, Serial No. 745,183 lin Germany September 30, 1933 2 claims. (ci. i12- ssi rlhis invention relates to a cutting device for buttonhoieor other sewing machines. It is known to positively push the knife of such machines into the material for the purpose of cuto ting and to pull it back into its inoperative position by a spring `after the cutting operation. It is likewise known to push the knife into the material and to positively pull it out of the material, the knife being operated by a cam disc. Compared herewith the invention consists in that the knife is positively driven into the material for cutting and also positively pulled out of the material after the cutting, the lever transmission actuating the knife being actuated by a crank driven from the main driving shaft through the intermediary ci a cam, and a safety device being provided which allows the knife only to he come operative when the cloth feeder is in the correct position and when the button hole is iin ished. lZtl-'iis is attained according to the invention in that the system of levers actuating the knife is coupled with Ia pivotally mounted lever moved up and down from the main driving shaft through the intermediary of a cam in such a manner that the knife is positively driven into the material for cutting and positively pulled out of the material, the coupling being controlled by a cam disc and. secured against premature coupling oy means of a safety device.

in embodiment of the invention is illustrated by way of example in the accompanying drawing, in whichz y Fig. i shows the machine with the cutting device in si-:le elevation.

Fig. 2 is a top plan view of Fig. l.

Fig. 3 shows a portion of the coupling lever in side elevation.

Fig. i is a part side elevation o the safety device for preventing premature coupling.

e A knife i isarranged on a rod 2 and guided on a bar The rod 2 is actuated icy a system of levers d, 5, "d, 1. The lever 1 is moved by a coupling arm d which is returned into its inoperative position shown in the drawing by means of a spring 9. The coupling arm B has a projection i@ on which a rod ill-bears in inoperative position. Discs l2 and i3 are fixed on this rod Il, whereas a disc i4 is loosely mounted thereon. .A spring i5, situated between the discs i2 and It, tends to maintain the rod il in the position illustrated. A rocker lever mounted in a bracket i6 bears with one arm I1 against the disc I3 and with its other arm I8 against a cam disc 20 keyed on a shaft I9. The shaft I9 is driven in known 55 manner at a suitable ratio of transmission from -lines in Fig. l.

the main driving shaft 21 through the intermediary of gear wheels 2i, 22, 23, 24, 25, 26. As the arm I8 slides on the cam disc 20, which rotates in the direction of the arrow 1:, the disc i3 and therefore the rod il will be shifted by the arm i1 in the direction of the arrow y against the action of the spring l5. The rod ii mounted in a bearing 23, owing to this shifting movement in the direction y, slides oi the extension itl and drops into the position indicated in dot-dash This bearing is rigid with a bracket dll fixed on the machine frame and the disc it is loosely mounted on the rod il. Consequently the disc ift is pressed by the spring i against the end ofthe bearing 28 and serves as an abutment for the spring i5.. The spring le might bear directly against the end oi the bearing 2d but as the rod il must swing up and down and. must consequently rit relatively loosely in the hearing it is advisable to interpose the/ disc iii between the bearing 2S and the spring` iti. The rod il is not mounted in a bearing at its other end because it must be able to move up and down with the end resting on the extension i@ of the lever Only-a bracket il is provided, d

sition under the action of the spring i5. The rod il, which is in the position shown in clot--dashl lines, will press the nose 3@ of the lever arm d Ftowards a bore 33 in an oscillatable strap 32.

This strap 32 is pivotally mounted in a bracket titl and is continually moved up and down from the main driving'shatfiil through the intermediary of a cam 36. During this up and down movement the nose on the arm t is pressed by the rod il towards the bore 33 in which it cannot, however, immediately engage owing' to the safety bar 31. After this pressure is exerted the arm 3l must rst complete its downward movement. During the upward movement the bar 311s pressed away from the bore 33 by the nose 30 against theaction of the spring 38, so that the nose 30 can engage in the bore 33. The knife I is thus positively coupled with the driving shaft 21. During the next downward movement of the arm 3l the material is pierced by the knife I and during. the succeeding upward movement it is pulled out of the material. The spring 9,

as already mentioned, returns then the coupling lever 8 with the nose 3U into their initial positions.

I cla-im:-

1. A cutting device on button hole and similar sewing machines, comprising in combination with the machine frame, a knife vertically reciprocable in said frame, a lever system connected with said knife, a main driving shaft journalled in said frame, a cam on said shaft, a crankactuated by said cam, a strappivotally mounted on said frame and oscillatable by said crank, a counter shaft driven by said main shaft, a second cam rotated by said counterl shaft, said strap having a bore, a coupling lever pivotally connected at one end with said lever system, a nose on the other end of said coupling lever adapted to engage the bore in said strap, a guide rod slidably mounted' on said machine frame, a'twoarmed lever bearing with one arm against said second cam and engaging with its other arm said guide rod, Said guide rod adapted to be longitudinally shifted. to the right by said cam, a spring on said guide roi-adapted to press said guide rod against said coupling lever and to oscillate said lever to cause said nose to engage said bore when the cam releases said rod, and a locking device on said strap adapted to prevent premature engagement oi' said nose in said bore.

2. A cutting deviceaon button hole and similar sewing'machines, comprising in combination with the machine frame, a knife vertically reciprocable in said frame, a lever system connected with said knife, a main driving shaft journalled in said frame, a cam on said shaft, a crank actuated by said cam, a sti-ap pivotally mountedon said frame and oscillatable by said crank, a counter shaft driven by said main shaft, a second cam rotated by said counter shaft, said strap having a bore, a coupling lever pivotally connected at one end with said lever system, a nose on the other end of said coupling lever adapted to engage the bore in said strap, a guide rod slidably mounted on said machine irame, a two-armed lever bearing with one arm against said second c'am and engaging with its other arm said guide rod, said guide rod adapted tobe longitudinally shifted to the right by said cam, a spring on said guide rod adapted to press said guide rod against said coupling lever and to oscillate said lever to cause said nose to engage said bore when the cam releases said rod, and a movable bar on said strap, and a spring supporting said ba'r so that it covers said bore, said bar adapted to yield against the action of said spring under the pressure oi' said nose during the oscillation of said strap to allow the engagement of said nose in said bore.

HERMANN PUDELKO. 

